Pressure coefficient

The pressure coefficient, which is often referred to as a pressure coefficient, is a dimensionless quantity from the aerodynamics, which often comes in the interpretation and analysis of the wings, but also in other areas of aerodynamics, eg in internal flows, are used.

It is used inter alia in order to describe the distribution of pressure on the wing of aircraft or graphically. Of the pressure distribution is defined as the pressure at all points on the entire surface of the airfoil. In relation to a certain point, the pressure coefficient ratio of the static pressure to dynamic pressure dar.

Formula for determining the Druckbeiwertes

Assume incompressible flow (Ma <0.3 )

These are:

  • = The measured static pressure at a certain point
  • = The static pressure in the inflow
  • = The density of the surrounding medium ( eg, air)
  • = Local speed amount of the surrounding medium (eg air ); instead is often used, or the velocity component in the x-direction.
  • = The flow velocity of the surrounding medium (analog and also common)

Importance of Druckbeiwertes

The denominator of the fraction, represents the dynamic pressure of the free incident flow, ie, 1 is the highest value that the pressure coefficient can achieve rigid body and without energy supply in an incompressible flow ( the stagnation point ). At the sign of the derivative of the pressure according to the run-length can be seen that the flow towards the inlet flow is accelerated or decelerated: negative signs mean acceleration ( ie pressure drop ), positive signs indicate regions where the flow is slowed down ( flow separation in friction -prone flow ) ( pressure increase).

Characterized in that the coefficient is related to the dynamic pressure, the distribution of the Druckbeiwertes a body does not change when the velocity, density or the static pressure of inflow changes. Moreover, the distribution is also valid for all geometrically similar body. From the pressure distribution around an airfoil that is, the actual pressures can be calculated for a wide range of flight speeds and heights.

These ratios are, strictly speaking, only in smooth incompressible flow, but also in the general case often applicable. They do not apply: Positions behind shocks in the boundary layer and flows with separations or variable point of transition between laminar and turbulent boundary layer.

  • Aerodynamics
  • Code ( Fluid Mechanics )
294868
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